The objective of this research is to understand the molecular structure and functional mechanisms of the photoreceptor cells responsible for visual excitation. The membrane structure of isolated rod outer segment (ROS) disks will be investigated by enzymatic modification using saccharidases, proteases and lipases followed by chemical characterization, high resolution X-ray diffraction and freeze fracture electron microscopy. The topology of lipid and protein functional groups will be studied with chemical labeling using membrane impermeable reagents and permeable analogs. The mechanism of disk-disk adhesion and the structure of the molecules responsible will be studied. This information may allow investigations of the involvement of the disk adhesion activity in retinal degeneration as well as the response to light. The functional light response of the disk membrane will be investigated (if an assay becomes available) after chemical and enzymatic structural lesions are introduced. Voltage sensitive dyes will be used to study the light response of the disk. Rhodopsin-rhodopsin interaction will be studied with regard to its role in the light response.